A few months ago, our local camera club was approached by an organisation that was promoting a fairly low key band (brat pack style music and I'd never heard of them). They were offering free entry to a concert, in exchange for being able to take photographs. The agreement however, was that they would own the copyright to the photos and would allow us to use them for internal club competitions. I was approached specifically, because the committee had seen some of my low light work, but I declined and explained why. If I was trying to get a foot on the ladder in that style of photography, then it may have been worth it to get my name known, but I was not going to give away copyright to photos I would have taken free of charge and pointed out it was exploitation. It would have been an interesting shoot, but I wasn't going to compromise my principles, even though I'm not a full time professional. For me, there has to be something in it for both parties and it is wrong to demand copyright. The legalities would probably be hazy, as there would probably be some sort of contract, with explicit agreement in the case of well known bands/brands. Ethically though, it is just wrong in my book.